What is the recommended dose of diltiazem (Calcium Channel Blocker) for a 77-year-old patient with Atrial Fibrillation (AFib) and Rapid Ventricular Response (RVR)?

Diltiazem Dosing for 77-Year-Old with Atrial Fibrillation and Rapid Ventricular Response

For acute rate control in a 77-year-old with AFib RVR, administer diltiazem 0.25 mg/kg (typically 15-20 mg) IV bolus over 2 minutes, followed by a continuous infusion of 5-15 mg/hour if needed. 1

Initial IV Bolus Dosing

• Standard dose: 0.25 mg/kg IV over 2 minutes 1
• Practical dosing: This translates to 15-20 mg for most adults 1
• Repeat dosing: If inadequate response, give an additional 0.35 mg/kg (20-25 mg) IV 15 minutes after the first dose 1

The 2014 AHA/ACC/HRS guidelines explicitly recommend IV beta blockers or nondihydropyridine calcium channel blockers (like diltiazem) as Class I, Level B evidence for slowing ventricular heart rate in the acute setting in patients without pre-excitation. 1

Continuous Infusion

• Maintenance infusion: 5-15 mg/hour IV, titrated to heart rate control 1
• Target heart rate: Aim for <100 bpm at rest, though <110 bpm may be acceptable in asymptomatic patients with preserved LV function 1

Age-Related Considerations for 77-Year-Old Patients

Elderly patients require careful monitoring but not necessarily dose reduction. 1 However, consider:

• Increased susceptibility: Older patients are more prone to orthostatic hypotension and bradyarrhythmias 1
• Comorbidities: Assess for heart failure, as diltiazem is contraindicated in decompensated HF 1
• Renal function: While the FDA label notes no specific data on renal impairment, careful titration is advised 2

Evidence on Lower Dosing Strategies

Recent research suggests lower doses may be equally effective with fewer adverse effects:

• Low-dose approach: Doses ≤0.2 mg/kg showed similar efficacy (70.5% therapeutic response) compared to standard doses (77.1%), but with significantly lower hypotension rates (18% vs 34.9%) 3
• Weight-based dosing: Doses ≥0.13 mg/kg achieved heart rate control faster (169 minutes) compared to <0.13 mg/kg (318 minutes), without increased hypotension 4

However, guideline-recommended dosing (0.25 mg/kg) remains the standard of care, as it is based on extensive clinical trial data and expert consensus. 1

Critical Safety Considerations

Absolute contraindications in this patient:

• Pre-excitation syndromes (WPW): Diltiazem can paradoxically accelerate ventricular response and is potentially harmful 1
• Decompensated heart failure: Nondihydropyridine calcium channel antagonists should not be used 1
• Severe hypotension or cardiogenic shock: Requires immediate cardioversion instead 1

Monitor closely for:

• Hypotension (most common adverse effect) 1
• Heart block 1
• Bradycardia 1

Alternative if Diltiazem Fails or is Contraindicated

• Beta blockers: Metoprolol 2.5-5 mg IV bolus over 2 minutes, up to 3 doses 1
• Amiodarone: 150 mg IV over 10 minutes for critically ill patients or those with heart failure 1
• Digoxin: 0.25 mg IV for patients with heart failure and no accessory pathway 1

Transition to Oral Therapy

Once rate controlled:

• Oral diltiazem: 120-360 mg daily (extended release formulation preferred) 1
• Immediate-release option: 30 mg four times daily initially, titrated to 180-360 mg/day in divided doses 2

Recent evidence suggests that transitioning to oral immediate-release diltiazem after IV bolus may be as effective as continuous IV infusion, with lower treatment failure rates (27% vs 46%) 5